The present invention relates generally to communications systems and, more particularly, to method and apparatus for handling downlink reference signal interference to PDSCH (Physical Downlink Shared Channel) in LTE (Long Term Evolution) CoMP (coordinated multipoint) transmission.
In 4G cellular networks such as Long Term Evolution-Advanced (LTE-A) network, macro base stations (BSs) are expected to coexist with pico BSs in order to improve coverage and spectral efficiency per unit area. Additionally, two or more macro and/or pico BSs may perform coordinated multipoint (CoMP) transmission to a user equipment (UE) on the cell-edge to mitigate the impact of interference. In such a heterogeneous deployment where a UE can receive signals from several macro and pico BSs, the issue of interference arising from reference signals is a major issue even when multiple BSs perform CoMP transmission.
Different from existing networks, a LTE-A network can reduce the impact of neighboring cell interference on cell-edge UEs via CoMP transmission. This requires multiple neighboring BSs cooperation to eliminate co-channel interference to cell-edge UEs (except for possible CRS interference). Several BS cooperation methods are provisioned in LTE-A including Joint transmission (JT). In JT, two or more neighboring BSs (macro or pico) simultaneously transmit to a UE, resulting in improved SNR of received data streams which improve its throughput. However, the interference from CRS REs still remains.